Polymerization behavior of silicic acid with Fe3+, Al3+, and Ca2+ coexisting ions

Silica dimerization in the presence of divalent cations

“…This rise in activation barrier in the presence of Ca demonstrates that the addition of divalent cations to the solution delays the dimerisation reaction. A similar observation was made experimentally by Shen et al 14 in which hindrance to the crystallisation process was demonstrated for polymerization of silicic acid in the presence of Ca 2+ , Al 3+ , and Fe 3+ . No significant change in the rate of polymerisation was observed in the experimental study for the case of Ca 2+ primarily because of a very low concentration of calcium chloride (0.02 M) added in comparison to the concentration of SiO 2 in silicic acid (1 M).…”

“…The thermodynamics of various steps like hydrolysis, solvation, dissociation, and condensation for silica formation initiating from tetraethylorthosilicate (TEOS) in the presence of monovalent cations (Na + and organic structure directing agents like tetramethylammonium (TMA), tetrapropylammonium (TPA) and tetrabutylammonium (TBA) ion) was also investigated. 13 Experimental polymerization of silicic acid in the presence of Ca 2+ , Al 3+ , and Fe 3+ was performed by Shen and co-workers 14 where they observed that the crystallization process is strongly hindered by the bivalent and trivalent cation. These experimental observations raises the question.…”

“…14 in which hindrance to the crystallisation process was demonstrated for polymerization of silicic acid in the presence of Ca 2+ , Al 3+ , and Fe 3+ . No significant change in the rate of polymerisation was observed in the experimental study for the case of Ca 2+ primarily because of a very low concentration of calcium chloride (0.02 M) added in comparison to the concentration of SiO 2 in silicic acid (1 M).…”

An efficient silica scale inhibiting strategy for geothermal systems: Combination of cationic and anionic polymers

“…The Fe element content in the scales was much higher than that of Ca and Mg elements, possibly due to the strong complexation ability of Fe 2+ or Fe 3+ with silicic acid. The Fe 2+ or Fe 3+ affected the polymerization process of silicic acid, resulting in their precipitation with silicic acid 44 . The C element contents of the three scales formed by not adding scale inhibitors, adding PEIE, and adding PEIE + AA/AMPS were 0%, 11.79%, and 0%, respectively, indicating the precipitation of PEIE and silica together, while the addition of AA/AMPS effectively prevented the precipitation of PEIE and silica.…”

“…In addition, a red shift was observed in the stretching vibrations of the hydroxyl (3650 cm À1 ) and ether groups (1180 cm À1 ) in the scale spectrum, which could be attributed to hydrogen bonding between the hydrogen atom of silicic acid and the oxygen atom of PEIE. 44 The moisture content of the scale was zero, eliminating the influence of water molecules on the infrared spectrum, especially the hydrogen bond. Furthermore, the intensity of peaks such as -NH-(3460 cm À1 ) and -CH 2 -(3460 cm À1 ) at the same positions were reduced, indicating the effect of silicic acid on the PEIE, suggesting the occurrence of a reaction between silicic acid and PEIE.…”